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Question: Error, (in eval/diff) invalid input: diff received (f1[i+1, i]-2*f1[i, i]+f1[i-1, i])/h^2, which is not valid for its 2nd argument

Question:Error, (in eval/diff) invalid input: diff received (f1[i+1, i]-2*f1[i, i]+f1[i-1, i])/h^2, which is not valid for its 2nd argument

9009134 110 Maple 2016
diff
February 04 2017
0

hi .in substuting in ode equation i encounter with error

Error, (in eval/diff) invalid input: diff received (f1[i+1, i]-2*f1[i, i]+f1[i-1, i])/h^2, which is not valid for its 2nd argument

please help me

thanksh_2.5_eq4.mw
 

 

restart; with(DEtools); with(plots); interface(rtablesize = 25); ode1 := -P1*(diff(f1(x, y), x, x, x, x, x, x)+diff(f1(x, y), y, y, y, y, y, y)+3*(diff(f1(x, y), x, x, x, x, y, y))+3*(diff(f1(x, y), x, x, y, y, y, y)))+P2*(diff(f1(x, y), x, x, x, x)+diff(f1(x, y), y, y, y, y)+2*(diff(f1(x, y), x, x, y, y)))-N_x*(diff(f1(x, y), x, x))-N_y*(diff(f1(x, y), y, y)); F1xx := i, proc (j) options operator, arrow; (f1[i+1, j]-2*f1[i, j]+f1[i-1, j])/h^2 end proc; F1yy := i, proc (j) options operator, arrow; (f1[i, j+1]-2*f1[i, j]+f1[i, j-1])/hy^2 end proc; F1xxxx := i, proc (j) options operator, arrow; (f1[i+2, j]-4*f1[i+1, j]+6*f1[i, j]-4*f1[i-1, j]+f1[i-2, j])/h^4 end proc; F1yyyy := i, proc (j) options operator, arrow; (f1[i, j+2]-4*f1[i, j+1]+6*f1[i, j]-4*f1[i, j-1]+f1[i, j-2])/hy^4 end proc; F1xxxxxx := i, proc (j) options operator, arrow; (f1[i+3, j]-6*f1[i+2, j]+15*f1[i+1, j]-20*f1[i, j]+15*f1[i-1, j]-6*f1[i-2, j]+f1[i-3, j])/h^6 end proc; F1yyyyyy := i, proc (j) options operator, arrow; (f1[i, j+3]-6*f1[i, j+2]+15*f1[i, j+1]-20*f1[i, j]+15*f1[i, j-1]-6*f1[i, j-2]+f1[i, j-3])/hy^6 end proc; F1xxyyyy := i, proc (j) options operator, arrow; (f1[i-1, j-2]-4*f1[i-1, j-1]+6*f1[i-1, j]-4*f1[i-1, j+1]+f1[i-1, j+2]-2*f1[i, j-2]+8*f1[i, j-1]-12*f1[i, j]+8*f1[i, j+1]-2*f1[i, j+2]+f1[i+1, j-2]-4*f1[i+1, j-1]+6*f1[i+1, j]-4*f1[i+1, j+1]+f1[i+1, j+2])/(hy^4*h^2) end proc; F1yyxxxx := i, proc (j) options operator, arrow; (f1[i-2, j-1]-2*f1[i-2, j]+f1[i-2, j+1]-4*f1[i-1, j-1]+8*f1[i-1, j]-4*f1[i-1, j+1]+6*f1[i, j-1]-12*f1[i, j]+6*f1[i, j+1]-4*f1[i+1, j-1]+8*f1[i+1, j]-4*f1[i+1, j+1]+f1[i+2, j-1]-2*f1[i+2, j]+f1[i+2, j+1])/(h^4*hy^2) end proc; eq := simplify(eval(ode1, {diff(f1(x, y), x, x) = F1xx(i, j), diff(f1(x, y), y, y) = F1yy(i, j), diff(f1(x, y), x, x, x, x) = F1xxxx(i, j), diff(f1(x, y), y, y, y, y) = F1yyyy(i, j), diff(f1(x, y), x, x, x, x, x, x) = F1xxxxxx(i, j), diff(f1(x, y), x, x, x, x, y, y) = F1yyxxxx(i, j), diff(f1(x, y), x, x, y, y, y, y) = F1xxyyyy(i, j), diff(f1(x, y), y, y, y, y, y, y) = F1yyyyyy(i, j)}))

Error, (in eval/diff) invalid input: diff received (f1[i+1, i]-2*f1[i, i]+f1[i-1, i])/h^2, which is not valid for its 2nd argument

  

NULL

 

expand(%)

i

 (1)

simplify(4*h^4*f3[i]*f4[i]*%)

4*h^4*f3[i]*f4[i]*i

 (2)

diff(f1(x, y), x, x, y, y, y, y)

diff(diff(diff(diff(diff(diff(f1(x, y), x), x), y), y), y), y)

 (3)

``

``

NULL


 

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